Remote-sensing Based Groundwater Recharge Estimates in the Danube-tisza Sand Plateau Region of Hungary

Mean annual recharge in the Danube-Tisza sand plateau region of Hungary over the 2000–2008 period was estimated at a 1-km spatial resolution as the difference of mean annual precipitation (P) and evapotranspiration (ET). The ET rates were derived from linear transformations of the MODIS daytime land surface temperature (Ts) values with the help of ancillary atmospheric data (air temperature, humidity, and sunshine duration). The groundwater under the sand plateau receives about 75 ± 50 mm of recharge annually (the plus/minus value is the associated error, resulting from an assumed 5% error in both the P and ET values), which is about 14 ± 9 % of the regional mean annual P value of 550 mm. The largest continuous region with elevated recharge rates (about 180 ± 50 mm a or 30 ± 8 % of P) occur in the south-western part of the plateau due to more abundant precipitation (around 580 mm a), while recharge is the smallest (about 40 ± 40 mm a or 7 ± 7 % of P) under forested areas. Typically, lakes, wetlands, river valleys, and certain afforested areas in the north-central part of the region act as discharge areas for groundwater.